The invention relates to a road finisher for laying carriageway surfacings by means of a floating laying beam which comprises a basic beam and extendable beams.
Road finishers for laying mixed material, varying according to the thickness to be laid, in particular in the form of asphalt mixes, are nowadays generally provided with floating laying beams, which comprise a centrally divided basic beam, to allow a roof profile to be set, and can be widened by extendable beams. The basic beam is articulated by means of tie bars on the chassis and its height above the underlying carriageway determines the laying height of the mixed material to be laid. The extendable beams are usually arranged behind the basic beam, offset in the direction of travel with respect to the basic beam, articulated on the tie bars, by the depth of said basic beam. For laying level surfacings, the rear edges of the bearing surfaces of the basic beam and of the extendable beams must be in the same plane (inclined with respect to the horizontal when laying a roof profile).
In the case of a floating laying beam, the bearing surface of the laying beam, resting on the material laid, has a positive setting angle in the direction of laying or direction of travel, to allow it to float on the material laid. This setting angle is dependent on various parameters, such as the load-bearing capacity of the mixed material to be laid, the weight of the laying beam, the degree of compaction achieved by the laying beam, the thickness of the course of the mixed material to be laid and the traveling speed.
Changes in the setting angle require a correction in the vertical position of the extendable beams in relation to the basic beam, to continue to ensure the levelness in the transverse profile. These changes in the setting angle may be performed manually by means of two spindles actuated by ratchets for each extendable beam.
These corrective measures are very laborious, especially since they may have to be performed on both extendable beams and often require recorrections, since the first adjusting step often only represents an approximation to the setting ultimately required.
DE 92 11 854 U1 discloses a road finisher in which, to avoid longitudinal steps in the surface contour of the material laid, a sensor is provided in the form of a pendulum on the basic beam, for the inclination of the latter. The sensor signal is used to adjust the extendable beams correspondingly by means of actuating drives. However, in this case, the inclination of the basic beam at the point of the sensor is measured with respect to the horizontal and not with respect to the actual laying plane, which may be inclined both in the direction of laying and transversely thereto with respect to the horizontal. This has the result that, on the one hand, the beam distortions occurring when traveling around bends during the laying of superelevations cannot be taken into account and that, on the other hand, changes in the load-bearing capacity of the material laid which may lead to changed floating of the laying beam, for example slumping of the laying beam, as well as elevations or depressions in the laying plane may lead to undesired step formation in the direction of laying. The occurrence of such changes would have to trigger in particular an immediate reaction, which permits no account to be taken of the laying rate and, in particular, of changes in the laying rate as well as the load-bearing capacity of the material laid, with the result that sufficiently accurate and uniform laying is not made possible.
The foregoing illustrates limitations known to exist in present road finishers. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully
In one aspect of the present invention, this is accomplished by providing a road finisher comprising: a chassis; a floating laying beam located behind the chassis; the laying beam comprising: a centrally divided basic beam; means for articulating the basic beam on both sides of the chassis by means of two tie bars; a pair of extendable beams, which can extend laterally from the basic beam; the basic beam and the extendable beams being arranged offset, one behind the other, in the direction of travel; and height-adjusting means for adjusting the height of the extendable beams vertically up and down, with respect to the basic beam.
The invention is explained in more detail below with reference to an exemplary embodiment represented in the accompanying illustration, diagrammatically showing a road finisher in side view.